Method of attaching rubber to leather



' Dec. 6, 1932. v, THOMAS I 1,890,345

METHOD OF ATTACHING RUBBER TO LEATHER Filed May 12, 1932,

Patented Dec. 6, 1932 UNITED STATES PATENT OFFICE ARTHUR VABNEY THOMAS, OF HANOVER, MASSACHUSETTS, ASSIGNOR T E. H. GLAPP p RUBBER COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHU- METHOD OF ATTACHING RUBBER TO LEATHER Application filed May 12,1932. Serial No. 610,826.

This inventionrelates to methods .of uniting leather and rubber to produce a composite sheet adapted for use as a shoe sole or the like. The principal purpose of the invention is to provide a simple, economical and efi'cient' process of intimately bonding the rubber and leather layers together by vulcanization without injuring the leather or impairing the vulcanizing reaction.

I am aware that several processes and expedients have heretofore been devised in an effort to provide a satisfactory bond or union between leather and rubber, but such methods have not proved entirely successful in commercial practice. Best results have been ob tained by vulcanizing a rubber compound to the leather sheet under conditions of heat and pressure, especially when a vulcanizable cement is coated upon the leather surfacebefore the rubber composition is applied thereto.

When leather is subjected to the heat and pressure of a hot vulcanizing press, the usual moisture and oil content of the leather sheet becomes vaporized and tends to inflate and burst the leather fibres when the vapors are inescapably confined within the press. The moisture content of the rubber compound and the vapors of vulcanization further complicate the problem and are likely to explode within the leather body,-thereby seriously injuring the composite product. For this reason some methods recommend that the leather be preheated approximately to vulcanizing temperature (approximately 320 F.) before the rubber compound is applied to the leather and thatthe material be placed in the press while the leather is hot and dry. However, such a practice is not satisfactory when a vulcanizable cement has been applied to the leather; for the cement becomes partially vulcanized during the preheating of the leather, thereby impairing its utility as an effective bond between the leather and rubber. Furthermore, preheating at high temperature tends to weaken and deteriorate the leather itself.

The present invention obviates this objection and also eliminates to a large extent special treatment of the leather before it is introduced to the vulcanizing press. The leather and rubber compound may be kept at normal room temperature, with the intermediate cement in an uncured state immedi ately before final vulcanization. My improved process provides for the escape of the vapors generated in the leather or rubber by introducing a wick-like layer of porous and absorbent fabric or the like which is placed against the outer, uncoated surface of the leather sheet before the leather is inserted (with the rubber compound) in the press. The wicking layer or pad may be a sheet of cotton duck or other suitable material which may be removed from the leather after vulcanization of the rubber to its opposite face.

In order that the leather will not contain excessive moisture at the time of vulcanization, I prefer to dry it at a moderate temperature and store it in a lime kiln until ready for use. The moisture which is absorbed by the leather after removal from the drying chamber will be driven off by the heat of vulcanization and allowed to escape through the wick-like pad. The vulcanizable cement, preferably rubber, latex, may be coated upon the leather before it is dried and will retain its adhesive qualities until the layer of rubber compound is applied to the coated surface. B0

The practice of the improvedpro-cess is illustrated more or less diagrammatically in the accompanying drawing, in which:

Fig. 1 is a sectional view showing a leather sheet 4; having a coating 5 of cement applied to one surface;

Fig. 2 is a similar view illustrating the layer 6 of rubber composition applied to the coat-ed surface of the leather; and

Fig. 3 shows the rubber and leather sec* tions placed between the platens 7 of a vulcanizing press with the wicking pad 8 of cotton duck applied to the back or uncoated face of the leather. It will be understood that the relative position of the rubber and wicking may be reversed, that is, the wicking may be above the leather and the rubber layer below it, as desired, in order to produce best results.

' vulcanization is efiected in the usual way, 10

the rubber and leather layers being united together and the cement coating penetrating into the pores of the leather securely to bond the opposed surfaces of the layers into an 5 inseparable union. The resulting composite sheet may be used for a variety of purposes and is particularly suitable for an outersole of ashoe. The layers of leather and rubber maybe formed of any desirable thickness, and a thin composite sole of this character may be easily attached by cement or by stitching. From the foregoing it is evident that the cardinal 'featureof the improved process consists in vulcanizing together a leather sheet and a layer of rubber composition in the presence ofa pad of textile fabric or other porous material which is applied to the outer or back side of the leathersheet, the vulcanization beingcarriedon under pressure at high temsaperature. The use of a suitable cement between the plied layers is a desirable adjunct of the process, and the preliminary step of drying the leather at moderate or relatively low temperature further contributes to the amefliciency of the process. The pad is not affected by the vulcanizing action and may be peeled away from the leather canization is complete.

I claim: Y 5 1. A process of uniting rubber and leather which consists in vulcanizing rubber composition to one side of a sheet of leather in the presence of a pad applied to the outer surface ofleather and adapted to allow the ai-yescape of vapors generated by vulcanization at high temperatures. I i

2. A'process of uniting rubber and leather which consists in coating one surface of a leather sheet with cement, applying rubber mi-{composition to the coated surface, placing a wick-like pad on the opposite side of the leather sheet, and vulcanizing the assembled parts at high temperature. i

, 3. A process-of uniting rubber and leather asg'which' consists in. applying rubber composition to a cement coated surface of a leather sheet while the leather is at normaltemperature', applying a piece of wicking material to the opposite surface of the leather sheet,

. cogrand vulcanizing the rubber to the leather in wicking and atrelatively the presence of the high temperature.

4. A process of uniting rubber and leather. by vulcanization at relatively high tempera tures, consisting in applying a vulcanizable cement to one surface of a leather sheet, spreading rubber composition upon the cemented surface while the leather is relatively cool, and placing a pad of textile fabric 1 against the outer surface of the leather during vulcanization.

5. A process of uniting rubber and leather by vulcanization at relatively high temperatures, consisting in first coating one surface 9510f the leather with cement, drying the leather opposite surface of the leather, and inserting after the vulunder moderately low temperature, applyin a layer of rubber composition to the coated surface, and subjecting the plied layers to vulcanization in the presence of a pad of wicklike material applied to the outer surface of the leather.

6. A process of uniting rubber and leather by vulcanization at relatively high temperatures, consisting in coating one surface of the leather witha vulcanizable ceincnt,drying 7 the leather at moderate temperature, applying a layer of rubber composition to the coated surface while the leather is relatively cool, placing a pad of, textilefabric against the 80 the plied leather, and rubber and the-padin a vulcanizing press. r a

7 A process of uniting-rubber and leather by vulcanization at relativelyihigh temperatures,'consisting in first drying the leather 7 one surface of theleather with cement, applying a layer of rubber composition to the coat-- ed surface, and subjecting the plied layers to vulcanization in the presence of a pad of m wick-like material applied to the outer surface of the leather. v i y 8. A process of uniting rubber and leather by vulcanization at relatively high tempera tures, consisting in drying the leather at moderate temperature, coating one surface of the leather with a vulcanizable cement, applying a layer of rubber composition to the coated surface while the leather is relatively cool, placing a pad of textile fabric against the m opposite surface of the leather, and insertin the plied leather. and rubber and the padin 

